PTL 1 discloses, as a wireless LAN system having a QoS function, for example, a system using extended MAC (Media Access Control) of IEEE802.11e.
In conventional MAC of IEEE802.11 standard, two functions, i.e., DCF (Distributed Coordination Access) and PCF (Point Coordination Channel Access) are defined. In the extended MAC of IEEE802.11e, EDCA (Enhanced Distributed Channel Access) having a QoS (Quality of Service) characteristic, which is obtained by extending the DCF, and HCCA (Hybrid coordinated function Controlled Channel Access) which is obtained by extending the PCF are defined.
The DCF and the EDCA are methods based on CSMA (Carrier Sense Multiple Access) and provide contention access means to a terminal. The PCF and the HCCA are access methods using a polling method and provide contention-free access means to a terminal. IEEE802.11e written standards disclose a reference scheduling method using the HCCA.
As a wireless access method extended in a multihop manner, other than the above method using the EDCA, a method of obtaining QoS with the use of polling is disclosed in PTL 2 and PTL 3.